1. Field of Invention
This invention relates to a waterbed mattress, and particularly to a waterbed mattress having multiple chambers useful for maintaining structural integrity of the mattress within a supporting frame.
Waterbeds have been long known for use in hospitals to prevent bed sores and to relieve burn victims. Moreover, waterbeds have in recent years attained general popularity. A waterbed will uniformly and comfortably support a person in a reclining position thereon. However, if a person ventures too close to the mattress perimeter, particularly if weight is concentrated at or near an edge abutting a support frame panel, the localized liquid tends to displace forming a depression. As a result, a portion of the body may be caught between the frame panel and mattress side panel, which could cause discomfort and result in possible injury.
2. Description of the Prior Art
Waterbed mattresses are known which utilize inflated air beam structure for rigidity and support. U.S. Pat. No. 3,766,579 to Shields, discloses a waterbed incorporating a selectively inflatable air structure. In the Shields patent, a waterbed mattress is described having an integral air frame about the periphery of the mattress wherein a water envelope is contained generally within the borders of an air filled frame. So far as could be determined, the patent does not suggest the use of a water and air filled mattress within a rigid frame, and therefore does not address the particular problems posed by a frame-enclosed mattress.
U.S. Pat. No. 3,864,768 to Fraige et al. describes a waterbed mattress adapted to be confined within a rigid box-like framework which comprises a water-inflatable bag-like enclosure and a float hingedly connected internally of the bag-like enclosure along one edge panel. The degree of support provided the upper edge of the water-filled mattress is apparently determined by the degree of inflation of the internal float tube which is buoyantly urged into the upper mattress corner. The float tube is an internal element or appendage separate from the the enclosure which merely floats in the liquid. In order to be operative as disclosed it necessarily must be filled with a gas such as air.